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Investigation on Improving Direct Discrete Method and its Application in Adjoint Diffusion Equation Numerical Solvers
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Numerical analysis method improvement is a topic of interest among all engineering disciplines. Regarding the fact that our ability to predict the behavior of a physical system is often limited by our computational resources, the efficiency of the employed numerical method is an important factor in the degree of approximation used in modeling. One of the recent numerical methods is the Cell Method (CM), which is also known as the Direct Discrete Method (DDM). This method combines some features of a variety of methods, especially finite volume and finite element, and gains some insight from the graph theory used in network analysis. The result is a method in which the set of equations which...
Development of Parallel Algorithm for Adjoint Optimization of Turbine Blade
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
This study develops an aerodynamic shape optimization code using parallel processing capability based on a gradient-based adjoint method. Calculation of the gradient of the objective function with respect to design variables is the most costly part of the gradient-based optimization algorithms. Applying adjoint methods, gradients can be calculated with solving some additional equations known as the "adjoint equations", instead of direct calculation. In this study, the blade shape optimization is performed by inverse design method and using steepest descent optimization algorithm. The objective function of inverse design problem is the desired blade surface pressure distribution. In each...
Calculation of the Scaling Factor for WWER-1000 Reactor (Boushehr)
,
M.Sc. Thesis
Sharif University of Technology
;
Vossoughi, Nasser
(Supervisor)
Three-dimensional Aerothermal Shape Optimization of Turbine Blade, Using Gradient Adjoint-based Methods
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
The most important challenge and the most time consuming part of the gradient based optimization algorithms in the aerodynamic shape optimization problems is the evaluation of the sensitivity of the objective function with respect to the design variables. The adjoint method which has been the subject of many research in the recent three decades, is capable of computing the complete gradient information needed for optimization by solving the governing flow equations and their corresponding adjoint equations only once, regardless of the number of design parameters. In this study, the continues adjoint equations for compressible inviscid and viscous flows are derived and the formulation of...
Development of Neutron Noise Simulator Based on the Boundary Element Method
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Aboulfazl (Supervisor)
Abstract
The present M.Sc. thesis consists of two sections including static calculation and neutron noise calculations in rectangular and hexagonal geometries. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equation is based on Boundary Element Method (BEM). The result are benchmarked against the valid results for BIBLIS-2D and IAEA -2D benchmark problem. In the second section, neutron noise calculation are performed for two types of noise sources, i.e. absorber of variable strength and Inadvertent Loading and Operation of a Fuel Assembly in an Improper Position (ILOFAIP). The...
Aerodynamic Optimization of Axial Compressors Using Adjoint Equations
, M.Sc. Thesis Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
In this study, aerodynamic shape optimization of axial compressors is considered. In order to optimization, one of the gradient based optimization algorithms, namely Adjoint method, is used. Recently, Adjoint method has been emerged as one of the reliable gradient based optimization algorithms in turbomahineries applications. Because this method is a gradient method of optimization, similar to the other entire gradient based algorithms, adjoint method also has a better convergence than non-gradient based optimization algorithms. In this work, aerodynamic shape optimization of two-dimensional cross section through a transonic axial compressor is studied. The process is considered for midspan...
Localization of a Postulated Noise in VVER-1000 Reactor Core Using Neutron Noise Analysis Methods
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION...
Accelerating MCNP using the Adjoint Flux
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor) ; Ayyoubzadeh, Mohsen (Co-Advisor)
Abstract
Nuclear engineering simulation requires computer codes which are capable of particle transportation and presenting valid answers. The Monte Carlo method is one of the particle transportation methods and the MCNP code is also a common and efficient code using Monte Carlo method. We usually come across statistical errors in Monte Carlo simulation for reducing which a number of methods have been presented which are called variance reduction methods. In simulating deep penetrating problems, analog Monte Carlo method is weak which leads to considerable error. The chosen variance reduction method for this study is the one which uses adjoint flux. In this study, a 3D deterministic transport code...
Aerodynamic Shape Optimization of Airfoils Using Adjoint Equations
,
M.Sc. Thesis
Sharif University of Technology
;
Mazaheri, Karim
(Supervisor)
Abstract
Adjoint-based aerodynamic optimization has drawn much attention, recently. It is based on gradient optimization procedures and requires the sensitivities of the design variables to find the optimized shape. The advantage of this method is that it estimates the sensitivities by solving an “adjoint equation”, instead of calculating them directly. In this thesis, the method is used to design airfoil shapes both in inviscid and viscous flows. In this regard, a flow solver and an adjoint solver have been developed. First, the validity of the flow solver is tested according to credited data form papers and softwares. Then, the optimizing program is tested using some inverse design problems....
Aerodynamic Optimization of Transonic Airfoils and Wings by Using Shock Control Bump, Suction and Blowing with Adjoint Method
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
Shock control bump (SCB) and suction and blowing are flow control methods used to control the shock wave/boundary layer interaction (SWBLI) in order to reduce the resulting wave drag in transonic flows. A SCB uses a small local surface deformation to reduce the shock-wave strength, while suction decreases the boundary-layer thickness and blowing delays the flow separation. Here, a single-point, a multi-point, and a robust optimization method are used to find the optimum design of SCB and suction and blowing. The flow control methods are used separately or together on two transonic airfoils i.e.; RAE-2822 and NACA-64A010 for a wide range of off-design transonic Mach numbers. The RANS flow...
Calculation of VVER-1000 reactor scaling factor for inference of core barrel motion
, Article Annals of Nuclear Energy ; Vol. 63 , 2014 , pp. 205-208 ; ISSN: 03064549 ; Vosoughi, N ; Sharif University of Technology
Abstract
To quantify the core barrel motion (CBM) in a pressurized water reactor, a scaling factor can be calculated to convert the Root Mean Square (RMS) value of the ex-core signals (%) to the core barrel motion amplitude (mil) (Thompson et al., 1980). In the current paper, a scaling factor is calculated using the direct and adjoint methods for a typical VVER-1000 reactor. The scaling factor is calculated using the perturbed parameters that result from CBM. The results show that the calculated scaling factors are not the same in one and two-dimensional modeling, and strongly depend on the ex-core detector location. The linearity assumption of relative detector response versus the small displacement...
Development of two-dimensional, multigroup neutron diffusion computer code based on GFEM with unstructured triangle elements
, Article Annals of Nuclear Energy ; Volume 51 , 2013 , Pages 213-226 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
2013
Abstract
Various methods for solving the forward/adjoint equation in hexagonal and rectangular geometries are known in the literatures. In this paper, the solution of multigroup forward/adjoint equation using Finite Element Method (FEM) for hexagonal and rectangular reactor cores is reported. The spatial discretization of equations is based on Galerkin FEM (GFEM) using unstructured triangle elements. Calculations are performed for both linear and quadratic approximations of the shape function; based on which results are compared. Using power iteration method for the forward and adjoint calculations, the forward and adjoint fluxes with the corresponding eigenvalues are obtained. The results are then...
Turbine blade aerodynamic optimization on unstructured grids using a continuous adjoint method
, Article ASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012, Houston, TX, 9 November 2012 through 15 November 2012 ; Volume 1 , 2012 , Pages 425-431 ; 9780791845172 (ISBN) ; Mazaheri, K ; Irannejad, A ; Sharif University of Technology
2012
Abstract
A gradient based optimization using the continuous adjoint method for inverse design of a turbine blade cascade is presented. The advantage of the adjoint method is that the objective function gradients can be evaluated by solving the adjoint equations with coefficients depending on the flow variables. This method is particularly suitable for aerodynamic design optimization for which the number of design variables is large. Bezier polynomials are used to parameterize suction side of the turbine blade. The numerical convective fluxes of both flow and adjoint equations are computed by using a Roe-type approximate Riemann solver. An approximate linearization is applied to simplify the...
Neutron noise simulation by GFEM and unstructured triangle elements
, Article Nuclear Engineering and Design ; Volume 253 , 2012 , Pages 238-258 ; 00295493 (ISSN) ; Vosoughi, N ; Sharif University of Technology
2012
Abstract
In the present study, the neutron noise, i.e. The stationary fluctuation of the neutron flux around its mean value, is calculated in 2-group forward and adjoint diffusion theory for both hexagonal and rectangular reactor cores. To this end, the static neutron calculation is performed at the first stage. The spatial discretization of equations is based on linear approximation of Galerkin Finite Element Method (GFEM) using unstructured triangle elements. Using power iteration method, forward and adjoint fluxes with the corresponding eigenvalues are obtained. The results are then benchmarked against the valid results for BIBLIS-2D and IAEA-2D benchmark problems and DONJON computer code. The...
Optimization of the direct discrete method using the solution of the adjoint equation and its application in the multi-group neutron diffusion equation
, Article AIP Conference Proceedings ; Volume 1389 , 2011 , Pages 1777-1781 ; 0094243X (ISSN) ; 9780735409569 (ISBN) ; Vosoughi, N ; Sharif University of Technology
2011
Abstract
Obtaining the set of algebraic equations that directly correspond to a physical phenomenon has been viable in the recent direct discrete method (DDM). Although this method may find its roots in physical and geometrical considerations, there are still some degrees of freedom that one may suspect optimize-able. Here we have used the information embedded in the corresponding adjoint equation to form a local functional, which in turn by its minimization, yield suitable dual mesh positioning
Optimization of neutron energy-group structure in thermal lattices using ultrafine bilinear adjoint function
, Article Progress in Nuclear Energy ; Volume 85 , 2015 , Pages 648-658 ; 01491970 (ISSN) ; Salehi, A. A ; Vosoughi, N ; Akbari, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
To solve neutron transport equation in multigroup approach, in addition to weighting function and number of energy groups, proper selection of the group boundaries have high importance for the accuracy of the calculations. In the current paper, the bilinear combination of forward and adjoint neutron spectra is used for the optimization of 69 energy group structure of WIMSD5 lattice physics code. To remedy the energy self-shielding effect, homogeneous adjoint and forward BN equations on an ultrafine energy group structure have been solved to obtain the ultrafine forward and adjoint spectra. The coarse group intervals are selected to have equal values of bilinear function in each...
The application of the gradient-based adjoint multi-point optimization of single and double shock control bumps for transonic airfoils
, Article Shock Waves ; 2015 ; 09381287 (ISSN) ; Nejati, A ; Chaharlang Kiani, K ; Taheri, R ; Sharif University of Technology
Springer New York LLC
2015
Abstract
A shock control bump (SCB) is a flow control method which uses local small deformations in a flexible wing surface to considerably reduce the strength of shock waves and the resulting wave drag in transonic flows. Most of the reported research is devoted to optimization in a single flow condition. Here, we have used a multi-point adjoint optimization scheme to optimize shape and location of the SCB. Practically, this introduces transonic airfoils equipped with the SCB which are simultaneously optimized for different off-design transonic flight conditions. Here, we use this optimization algorithm to enhance and optimize the performance of SCBs in two benchmark airfoils, i.e., RAE-2822 and...
Galerkin and Generalized Least Squares finite element: A comparative study for multi-group diffusion solvers
, Article Progress in Nuclear Energy ; Volume 85 , 2015 , Pages 473-490 ; 01491970 (ISSN) ; Saadatian Derakhshandeh, F ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Abstract In this paper, the solution of multi-group neutron/adjoint equation using Finite Element Method (FEM) for hexagonal and rectangular reactor cores is reported. The spatial discretization of the neutron diffusion equation is performed based on two different Finite Element Methods (FEMs) using unstructured triangular elements generated by Gambit software. Calculations are performed using Galerkin and Generalized Least Squares FEMs; based on which results are compared. Using the power iteration method for the neutron and adjoint calculations, the neutron and adjoint flux distributions with the corresponding eigenvalues are obtained. The results are then validated against the valid...
Propagation noise calculations in VVER-type reactor core
, Article Progress in Nuclear Energy ; Volume 78 , January , 2015 , Pages 10-18 ; 01491970 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Neutron noise induced by propagating disturbances in VVER-type reactor core is addressed in this paper. The spatial discretization of the governing equations is based on the box-scheme finite difference method for triangular-z geometry. Using the derived equations, a 3-D 2-group neutron noise simulator (called TRIDYN-3) is developed for hexagonal-structured reactor core, by which the discrete form of both the forward and adjoint reactor dynamic transfer functions (in the frequency domain) can be calculated. In addition, both types of noise sources, namely point-like and traveling perturbations, can be modeled by TRIDYN-3. The results are then benchmarked in different cases. Considering the...
Localization of a noise source in VVER-1000 reactor core using neutron noise analysis methods
, Article International Conference on Nuclear Engineering, Proceedings, ICONE, 17 May 2010 through 21 May 2010 ; Volume 2 , May , 2010 ; 9780791849309 (ISBN) ; Vosoughi, N ; Zahedinejad, E ; Nuclear Engineering Division ; Sharif University of Technology
2010
Abstract
In this paper, localization of a noise source from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The boxscheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. The dynamic state is assumed in the frequency domain which leads to discarding of the time disrcetisation. The developed 2-D 2- group neutron noise simulator calculates...